Metabolomic Analysis of Hexagenid Mayflies Exposed to Sublethal Concentrations of Naphthenic Acid.

The oil sands region in northeastern Alberta, Canada contain approximately 165 billion barrels of oil making it the third largest oil reserves in the world. However, processing of extracted bitumen generates vast amounts of toxic byproduct known as oil sands process waters. Naphthenic acids and associated sodium naphthenate salts are considered the primary toxic component of oil sands process waters. Although a significant body of work has been conducted on naphthenic acid toxicity at levels comparable to what is observed in current oil sands process waters, it is also important to understand any impacts of exposure to sublethal concentrations. We conducted a microcosm study using the mayfly Hexagenia spp. to identify sublethal impacts of naphthenic acid exposure on the survival, growth, and metabolome across a concentration gradient (0-100 µg L-1) of sodium naphthenate. Nuclear magnetic resonance-based metabolomic analyses were completed on both the polar and lipophilic extracted fractions of whole organism tissue. We observed a positive relationship between sodium naphthenate concentration and mean principal component score of the first axis of the polar metabolome indicating a shift in the metabolome with increasing naphthenic acid exposure. Eleven metabolites correlated with increased naphthenic acid concentration and included those involved in energy metabolism and apoptosis regulation. Survival and growth were both high and did not differ among concentrations, with the exception of a slight increase in mortality observed at the highest concentration. Although lethal concentrations of naphthenic acids in other studies are higher (150-56,200 µg L-1), our findings suggest that physiological changes in aquatic invertebrates may begin at substantially lower concentrations. These results have important implications for the release of naphthenic acids into surface waters in the Alberta oil sands region as an addition of even small volumes of oil sands process waters could initiate chronic effects in aquatic organisms. Results of this research will assist in the determination of appropriate discharge thresholds should oil sands process waters be considered for environmental release.

Assessing natural recovery from contaminants in a river using sediment chemistry and toxicity from different depth ranges.

To determine whether natural recovery was occurring in a depositional area of the St. Marys River (Ontario, Canada) known as East Bellevue Marine Park (EBMP), sediment was collected from two depth ranges, 0-5 cm and 0-10 cm, and subjected to a series of laboratory toxicity tests and chemical analysis. Toxicological responses (survival, growth, reproduction, development) of four benthic invertebrates and the fathead minnow were compared at test vs. reference sites using univariate and multivariate (ordination) techniques. Temporal trends in sediment chemistry and invertebrate toxicity were examined with time series data from 2008 through to 2018. Polycyclic aromatic hydrocarbons (PAHs; ≤ 37 mg/kg) and petroleum hydrocarbons (PHCs; ≤ 6266 mg/kg) were elevated in EBMP compared to reference sites (PAHs, ≤ 1.6 mg/kg; PHCs ≤ 180 mg/kg). Comparatively, the 0-5 cm sediment layer had lower concentrations of all contaminants than the 0-10 cm layer at three of four test sites. Over time, contaminant concentrations have mostly remained stable or have decreased. There were no significant differences in survival, growth, or development of the larval fish in EBMP compared to the upstream reference sites, and no differences between sampling depths. However, most EBMP sediments were toxic to invertebrates, driven by reduced reproduction by the worm Tubifex and reduced survival by the amphipod Hyalella. Among habitat variables, a combination of different classes of compounds based on ordination scores (PHCs, oil and grease, metals) was most strongly correlated to toxicological response. There was little to no difference in toxicity between sampling depths based on integrated endpoint response; however, individual endpoints showed mostly greater toxicity from exposure to the 0-10 cm layer. Over time, toxicity has mostly remained stable or showed improvement. These results provided some positive indications that gradual natural recovery is occurring in EBMP.

Comparative toxicity of azo dyes to two infaunal organisms (Hexagenia spp. and Tubifex tubifex) in spiked-sediment exposures.

Azo dyes are synthetic compounds used as industrial colorants, and some are predicted to be inherently toxic, bioaccumulative, and/or persistent based upon their chemical composition. This study addresses data gaps in current research which include the need to evaluate the toxicity of hydrophobic azo dyes to benthic invertebrates. The toxicity of a solvent dye, Sudan Red G (SRG), and two disperse dyes, Disperse Yellow 7 (DY7) and Disperse Orange 13 (DO13), to Hexagenia spp. and Tubifex tubifex was assessed in spiked-sediment exposures. The dye compounds appeared to degrade readily in the equilibrium and exposure periods, suggesting a limited persistence of the parent compounds in the environment under test conditions. Although azo dye degradation products could not be reliably quantified, one was detected in DY7 sediment samples that elicited toxic effects to Hexagenia and Tubifex, providing evidence that DY7 degrades. Hexagenia survival and growth endpoints responded with similar sensitivity to the dyes, but DY7 was the most toxic, with a 21-day IC25 (concentration associated with 25% inhibition) for growth of 9.6 µg/g. Comparatively, Tubifex reproduction was the most sensitive endpoint for all dyes with 28-day IC25s for young production ranging from 1.3 to 11.8 µg/g. At sublethal concentrations, toxic effects to Tubifex differed between dyes: the solvent dye exerted an effect primarily on gametogenesis (cocoon production), while disperse dyes, most notably DY7, caused effects on embryogenesis (development of worm inside the cocoon). This study indicates that there could be potential hazard to oligochaetes based on the observed effect concentrations, but given the lack of environmental measurements, the risk of these compounds is unknown. Further research is required to determine if degradation products were formed in all dye samples and whether toxicity was caused by the parent molecules, which have limited persistence under test conditions, or by their degradation products. To avoid underestimating toxicity, this study stresses the need to use an infaunal deposit feeder such as the oligochaete Tubifex in sediment toxicity assessments where highly hydrophobic compounds are present.

Toxicity of sediment-associated substituted phenylamine antioxidants on the early life stages of Pimephales promelas and a characterization of effects on freshwater organisms.

Substituted phenylamine antioxidants (SPAs) are high production volume chemicals that are incorporated into a variety of commercial products (e.g., polymers, dyes, lubricants). There are few data on chronic toxicity of SPAs to fish and no data on the toxicity of SPAs to the early life stages of fish. The physicochemical properties of SPAs would suggest that if they were to enter an aquatic ecosystem they would partition into sediment. Therefore, the present study focused on investigating the chronic effect of sediment-associated SPAs to the early life stages of the fathead minnow (Pimephales promelas). Eggs and larvae were exposed to sediment spiked with diphenylamine (DPA), N-phenyl-1-napthylamine (PNA), N-(1,3-dimethylbutyl)-N'-phenyl-1,4-phenylenediamine (DPPDA), or 4,4'-methylene-bis[N-sec-butylaniline] (MBA). The most sensitive endpoint for DPA, PNA, and DPPDA was total survival with 21-d median lethal concentrations (LC50s) based on concentration in overlying water of 1920, 74, and 35 µg/L, respectively. The most sensitive endpoint for MBA was growth with a 21-d median effective concentration (EC50) of 71 µg/L. The same endpoints were the most sensitive in terms of concentrations of DPA, PNA, DPPDA, and MBA in sediment (101, 54, 111, and 76 µg/g dry wt, respectively). Species sensitivity distributions (SSDs) were constructed for each SPA based on acute and chronic toxicity data generated in the present study and found in the literature. Overall, P. promelas was in the midrange of chronic sensitivity, with the most sensitive species being Tubifex tubifex. The SSDs indicate that DPA based on concentration in water is the least toxic to aquatic biota of the 4 SPAs investigated. The constructed SSDs indicate that a concentration in water and sediment of 1 µg/L and 1 µg/g dry weight, respectively, would be protective of >95% of the aquatic species tested. Environ Toxicol Chem 2017;36:2730-2738. © 2017 SETAC.

Sediment contamination in Lyons Creek East, a tributary of the Niagara River: part I. Assessment of benthic macroinvertebrates.

Sediments in Lyons Creek East (Welland, Ontario), a tributary of the Niagara River and part of the Niagara River Area of Concern, which exceed screening-level environmental-quality criteria for multiple contaminants, were assessed for biological impacts using information from multiple lines of evidence. An initial chemical survey indicated the primary contaminants of concern to be polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), zinc, and p,p'-DDE due to frequent exceedences of sediment guidelines. A subsequent study focused on the chemical composition of sediment, status of benthic invertebrate communities, contaminant bioaccumulation in resident benthos, and sediment toxicity to laboratory-exposed organisms. Chemical and biological conditions in the creek were compared with those in reference creeks using both multivariate (cluster analysis and ordination) and univariate (regression) techniques. Sediment PCBs (≤ 19 µg/g), PAHs (≤ 63 µg/g), and Zn (≤ 7969 µg/g) were increased above the sediment-quality guidelines along most of the creek; however, the upper 1.5 km portion of the creek was the most highly contaminated and therefore the main focus for biological study. Although severe toxicity was evident at several locations in the upper creek, resident benthic communities were minimally affected by sediment contamination. The cause of toxicity was likely related to a combination of stressors, including PCBs, PAHs, and metals. Due to its biomagnifiable nature, bioaccumulation focused on PCBs; concentrations in resident macroinvertebrates were ≤ 2 orders of magnitude greater than those found in reference creeks and were above tissue residue guidelines, indicating a potential risk for consumers of benthos. This risk was not limited to the upper 1.5 km where other effects were seen.

Sediment quality in Rio Guadiamar (SW, Spain) after a tailing dam collapse: contamination, toxicity and bioavailability.

An integrated assessment of sediment quality in the Guadiamar River after a mining spill was conducted. The concentration of different metals and other conventional parameters were measured in sediments located along the river. Four sediment toxicity tests (Hyalella azteca 28-day survival and growth test; Chironomus riparius 10-day survival and growth test; Hexagenia spp. 21-day survival and growth test; and Tubifex tubifex 28-day reproduction and survival test) were carried out to determine the effects associated with the accidental spill. The geochemical fractions of 6 metals (Fe, Mn, Zn, Cu, Pb, and Cd) were determined to establish the bioavailability of the metals. The relationship found in the concentrations of metals associated with the mobile fractions of the sediments in the sites studied is similar to the toxic mud from tailing pond and confirms that the toxic effects are associated with the metals Zn and Cd originating from the spill.

The relative sensitivity of four benthic invertebrates to metals in spiked-sediment exposures and application to contaminated field sediment.

The relative sensitivity of four benthic invertebrates (Hyalella azteca, Chironomus riparius, Hexagenia spp., and Tubifex tubifex) was determined for Cd, Cu, and Ni in water-only and in spiked-sediment exposures. Survival (median lethal concentrations [LC50s] and the concentrations estimated to be lethal to 25% of test organisms [LC25s]), and endpoints for growth and reproduction (mean inhibitory concentrations [IC25s]) were compared. The sensitivities differed depending on the species and metal, although some trends emerged. In water-only exposures, H. azteca is the most sensitive species to cadmium and nickel, with mean LC50s of 0.013 and 3.6 mg/L, respectively; C. riparius is the most sensitive species to copper, with a mean LC50 of 0.043 mg/L. In the spiked-sediment exposures, the order in decreasing sensitivity to copper is Hyalella = Hexagenia < Chironomus < Tubifex for survival and growth/reproduction. For cadmium, the order in decreasing sensitivity is Hyalella = Chironomus < Hexagenia < Tubifex, and for nickel is Hyalella << Hexagenia < Chironomus < Tubifex. Chironomus riparius and Hexagenia spp. survival can be used to distinguish between toxicity caused by different metals. Species test responses in field-collected sediment(Collingwood Harbour, ON, Canada) were examined in an attempt to determine the causative agent of toxicity throughout, using the established species sensitivities. Sediment toxicity was categorized first by comparing species responses to those established for a reference database. Test responses in the field-collected sediment do not support causality by Cu, a suspected toxicant based on comparison of sediment chemistry with sediment quality guidelines.